The removal of tissue from the prostate gland or from tumours within the bladder is a common urological procedure. It is normally carried out through the urethra using a slender metal instrument which allows the urological surgeon to see the inside of the urethra or bladder. The surgeon can perform a number of procedures using special instruments which are inserted through a specially designed channel within the instrument. Such procedures for removing prostate tissue or bladder tumours are known as trans-urethral resection of the prostate (TURP) or trans-urethral resection of the bladder (TURB) respectively. The instrument used to remove pieces of tissue from the prostate or tumours from the bladder is called a resectoscope and it commonly uses a loop of wire at the end which cuts through the tissue using electro-surgery. This results in pieces of tissue being cut free which are commonly referred to as "chips" or fragments. The whole procedure of removing these fragments is carried out within a liquid environment of glycine; glycine is chosen for its electrical non-conductivity so that it does not interfere with the electro-surgical process. The fragments are released into the liquid and must be removed along with any blood which may be released as the tissue is cut.
The traditional method of removing the fragments and washing away the blood is by means of an Ellik evacuator. This consists of a glass bulb which has upper and lower chambers with a constriction between the two. The top chamber has an outlet on one side which connects to the sheath of the resectoscope be means of a piece of rubber tubing, and an outlet on the other side to which a rubber bulb is attached. With the apparatus completely filled with liquid, the surgeon compresses the rubber bulb to drive liquid through the resectoscope into the patient's bladder. The bulb is then released to draw the liquid back from the bladder bringing with it some of the fragments and blood. The fragments enter the top chamber of the Ellik evacuator with the expectation that they will settle into the lower chamber before the bulb is compressed again. However the flow of liquid across the top of the chamber tends to create a vortex within the glass chambers and this can result in some of the fragments being disturbed and returned to the bladder together with those that may still be in the upper chamber. This is clearly undesirable and results in an inefficient process that requires the evacuator to be emptied at frequent intervals as well as requiring a large number of evacuations to be performed.
Many attempts have been made to improve on the Ellik evacuator, but none has proved satisfactory. In one design the evacuator involves an open-ended tube which extends through a screw cap into a compressible bottle of plasticised polyvinyl chloride. The tube, which extends nearly half the height of the bottle, has a large number of holes through its wall so that when the bottle is squeezed, liquid is driven through these holes as well as through the larger open-end of the tube, to be expelled from the tube into the sheath of the resectoscope and thence into the bladder. As the bottle is released, the liquid returns from the bladder bringing some of the fragments with it, and these fragments which in general cannot pass through the holes, pass into the bottle from the open end of the tube. The intention is that the fragments should settle to the bottom of the bottle, and that when the bottle is subsequently compressed fragments that have not settled will be filtered out as the liquid containing them passes through the holes in the tube-wall. However, there is nothing in this form of apparatus to prevent fragments from entering the open end of the tube and so be returned to the bladder via the resectoscope.